Use purge option where appropriate.

* modules/jenkins/manifests/master.pp
* modules/jenkins/manifests/slave.pp: Recursively purge the
slave_scripts dir. This will remove old slave scripts.

* modules/openstack_project/manifests/gerrit.pp: Recursively purge the
gerrit ACLs dir. This will remove old and renamed ACL files.

* modules/openstack_project/manifests/nodepool.pp: Recursively purge the
nodepool scripts dir. This will remove old and renamed nodepool scripts.

* modules/openstack_project/manifests/static.pp: Recursively purge the
devstack log help files. This will remove old and renamed help files.

Change-Id: If739b274075781dcd0d0836bca96dd1764c6ee19
Merge "Use purge option where appropriate."